1. Field of the Invention
The present invention relates to a ferrite material having a little change in permeability in a wide temperature range, that is, a ferrite material having a small absolute value of temperature coefficient, or the like.
2. Description of the Related Art
In order to obtain a Ni—Cu—Zn ferrite material having a low temperature coefficient, the following proposals have been made so far.
Japanese Patent Laid-Open No. 2002-60224 describes a ferrite material, which comprises, as main constituents, iron oxide in a range between 46.0 and 49.0 mol % in terms of Fe2O3, copper oxide in a range between 4.0 and 11.0 mol % in terms of CuO, zinc oxide in a range between 30.1 and 33.0 mol % in terms of ZnO, and the balance being nickel oxide, and further comprises, as additives, cobalt oxide in a range between 0.005 and 0.03 wt % in terms of CoO, bismuth oxide in a range between 0.1 and 0.5 wt % in terms of Bi2O3, silicon oxide in a range between 0.1 and 0.6 wt % in terms of SiO2, and magnesium oxide in a range between 0.05 and 1.0 wt % in terms of MgO.
Japanese Patent Laid-Open No. 2001-348226 describes a ferrite material, which comprises, as main constituents, iron oxide in a range between 40 and 46 mol % in terms of Fe2O3, zinc oxide in a range between 25.1 and 30 mol % in terms of ZnO, nickel oxide in a range between 10 and 25 mol % in terms of NiO, and the balance being copper oxide, and further comprises, as additives, bismuth oxide in a range of less than 2 wt % in terms of Bi2O3, and cobalt oxide in a range of 0.1 wt % or less in terms of Co3O4.
Moreover, Japanese Patent Laid-Open No. 5-3112 describes a ferrite material, which comprises Ni—Cu—Zn ferrites as main constituents, comprising Nb in a range between 0.2 and 0.8 wt % in terms of Nb2O3, Ta in a range between 0.3 and 1.2 wt % in terms of Ta2O5, and Mo in a range between 0.15 and 1.35 wt % in terms of MoO3.
Main constituents of a Ni—Cu—Zn ferrite material are controlled, and further, the above additives are contained in the ferrite material, so that the absolute value of a relative temperature coefficient of an initial permeability (hereinafter referred to as αμir) is set at 5 ppm/° C. or less in Japanese Patent Laid-Open Nos. 2002-60224 and 2001-348226, and so that the absolute value of αμir is set at 1.3 ppm/° C. or less in Japanese Patent Laid-Open No. 5-3112.
However, in Japanese Patent Laid-Open Nos. 2002-60224 and 2001-348226, αμir is a value obtained between 20° C. and 60° C., and in Japanese Patent Laid-Open No. 5-3112, αμir is a value obtained between −25° C. and 85° C. Thus, a ferrite material is desired, which has a small absolute value of αμir in a wider temperature range such as a range between −40° C. and 160° C.
The present invention has been made to achieve such technical objects. It is an object of the present invention to provide a ferrite material having a small absolute value of αμir in a wide temperature range between −40° C. and 160° C.